While I'm pro-union in general, not all unions are equal. Some are powerful. Some are weak. Back in the 1990s I worked part-time for a unionized grocery store chain and was a member of the UFCW. There were four contract negotiations while I was there, and each time the union rolled over and approved pay cuts, decreasing the top pay rate and slashing insurance benefits. Long-time workers saw their pay cut from $11.11 an hour to $7.50 an hour over the course of a few years. Many left or took an offered buyout during the last pay cut. The last cut finally affected me as well and I took that same buyout.
No one at my store liked the union, and I have to admit that it turned me off of unions for a while. The UFCW was weak and had little bargaining power over a company that was losing money and, as we later learned, was being embezzled dry by its president.